The turbocharger failed on my 2001 B5 /AWM/ 1.8. Filled the entire exhaust system with oil. Replaced the turbo and soaked the cat in a bucket of soapy water overnight. Finally quit smoking after driving about 50 miles and burning off all the oil in the exhaust. But, I am getting the dreaded CEL with a Code P0420. Installed a spacer on the post cat O2 sensor but still getting the P0420 code. Now I am considering replacing the cat. The OEM Genuine Audi cat is crazy expensive. Looking for a quality aftermarket cat that will hopefully keep the P0420 code away. Any suggestions?